Aircraft trainer



R. C. DAVIS ET AL Aug. 15, 1950 AIRCRAFT TRAINER Filed June 50, 1944 6 Sheets-Sheet 1 H MIMI Wq \N 3 R. C. DAVIS ET AL Aug. 15, 1950 AIRCRAFT TRAINER 6 Sheets-Sheet 2 Filed June 30, 1944 E $33 mom thumb 65 a8 Qhm INVENTORS:

l! E BOHMAN R. c. 0.4 ws 0. 1:. GERMANTON 6? 6. M'

ATTORNEY AIRCRAFT TRAINER Filed June so, 1944 6 Sheets-Sheet 3 Aug. 15, 1950 R. c. DAVIS ETAL AIRCRAFT TRAINER 6 Sheets-Sheet 4 Filed June 30, 1944 Nkk MR:

mom A HES R at Nix QR H ER 7 V E BOHMAN /NVENTOR$ R. CDAV/S N m M M m 6 B ATTORNEY Aug. 15, 1950 R. c. DAVIS ET AL AIRCRAFT TRAINER Filed June 50, 1944 6 Sheets-Sheet 5 V.F. BOHMAN INVENTORS R.C.DAV/S By C.E.GERMANTON ATTORNEY R. C. DAVIS ET AL AIRCRAFT TRAINER 6 Sheets-Sheet 6 Filed June 30, 1944 BOHMAN R. 0. DA ws 0. E. GERMANTON INVENTORS:

ATTORNEY Patented Aug. 15, 1950 Richard C. Davis, Great Neck, and Vincent F. Bohman, Astoria, N. Y., and Charles E. Germanton, Summit, N. J., assignors to Bell Telephone Laboratories, Incorporated, New York,

N. Y., a corporation of New York Application June so, 1944, serial No. 542,984

This invention relates to aircraft trainers and more particularly to apparatus for simulating, "in the operation of the controls, the reactions 'which the pilot would receive in the operation of an actual aircraft. I I

In the controlof an aircraft the pilot feels resistance to the operation of thestick or yoke, of the aileron wheel if provided separate from ,theyoke, and of therudderpedalswhich varies inaccordance with the pressure of the slip stream against-the control surfaces of the elevator, of the aileron and of the rudder and is a function of the air speed of the aircraft and of the-attitude of the aircraft, For example, when the pilot pulls the stick back toexecute a climbing maneuver or pushes it forward" to execute a diving maneuver, the elevator is moved outof its normal plane and therefore becomes engaged by the slip stream to a greater 'or lessextent dependent upon the steepness of the intendedclimb or dive, and thepressure of jthe slipstream upon 1 the elevator surface reacts as ,ares'istance to the movement of the elevator whichistransferred to the stick as a resistance to be overcome by'the pilot in moving the stick. Similarly on 'a .correctly, executed turn the movement of the rudder from its normal straight flight position sub jects its surface to the pressure of the slip 18 Claims. (C1. 3512) constant effort to maintain the aircraftfin a level straight line' flight, its control surfaces are provided with trimming tabs which may be adjusted" by trimming wheels placed near the pilots seat. For example, if the aircraft is either hnosef heavy or tail heavy and therefore ha's a tendency to pitch, the trimming tabs hinged, :to

the trailing edge of the elevator may be moved by the elevator trimming wheel resuItingLin-increasing the camber of the, airfoil 'so that if-the tab is moved down the elevator surface is caused to move up to cause the nose of the aircraft to for level flight has been attained. Similarly,

rise, or if the tab is moved up the elevator surface is caused'to move down to cause thenose of the aircraft tofallfuntilthe correctattitude if the aircraft has a tendency to yaw in one direction .or the other ,the'trimming tab hinged to the trailing edgeof the rudder may be moved by the rudder trimming wheel" resulting in inlcreasing the camber ofthe airfoil so t hat the 'f'slip .stream encountering the rudder trimming .aircraft to fly a straight course.

' stream whichreacts as a resistance tothe movement of the rudder whichis transferred to. the rudder pedals as a resistanceto be overcome by the pilot in their movement, andgthe movement of the ailerons from their normal positions subjectsItheir surfaces to a change inpressure, from the slip stream which reactsias aresistance .to their movement which'is transferred to the aileron control wheel'or stichias'aresistance to be overcome by the, pilot in the movement'of the .wheel or tick. Also, since somejelevator control,

is also required on a correctly executed turn to keep theinose ofthe aircraft up; thefpilot will encounter some resistance to the forward movement of the stick: fAt other times the movement *of thecontrols does not meet as greatjife'sis'taiice transmitted themes by pressures applied against the controlsurfac'es Th'e resistance to the movement of the'control surfaces 'is a-function of the air-speed of the aircraft and, in general, increases .as the air'speed'increases; -r-' 1 Due to the disposal of the live, fuel, or;-, cargo loads in an aircraft, the aircraftmay not be in correct balance around its axes for straight level flight. In order that it may be possible to properly balanceor trim the aircra ftand thus relieve the pilot from the necessity of exercising a of the trimming wheels,

tab will move the rudder sufficiently to cause the aircraft has a tendency to roll about itslongitudinal axis, trimming tabs hinged to thetrailing edges ofthe aileronmay be movedby, the

' aileron trimming wheel resulting in increasing the camber of theairfoilssothat the slip stream encountering such tabs will 'move the ailerons sufiiciently to cause the aircraft to assume alevel position with respect to its longitudinal} axis.

The pilot may alsov use the trimming wheels to reduce the effort required to move,the-;convtrols since the setting ofnthel trimming tabs is effective to ,cause the slip stream. to move the large control surfaces to which the tabs; are

secured. If, for example, the'aircraft issto-be 5 flown on a climbing flight to gain a high altitude ,the pilotmay pull back the stick cryokeuntil l the aircraft isclimbing at a :desired steady rate ,of climb and then thetpilot may set the elevator ,trimmingtabs so that they will-hold the elevator in the required-- position without further effort H It is an object of the simulate in an aircraft trainer the changeifin loadings or resistances to the movement of the controls, of an aircraft undendifferentflight onthepart of the-pilot. a

presentv invention {gto conditions.

,A further object of the invention to simulate in an aircraft trainer the efiect onlthe controls of an actual aircraft incident to the oper'ation To attain these objects the-trainer with mechanisms which apply loadings to the elevator control stick or yoke, to the aileron control wheel and. to the rudder control pedals and with a further tensioning mechanism which varies the loadings in accordance with the indi- 5 cated air speed of the simulated flight. Each loading mechanism omprisesi1 a1qing pulley which may be turned by the control member with which the loading mechanism is associated. as, for example, by the movement of the stic'li l or yoke, which loading pulley turns one. or

the other direction dependent on th e dir of movement of the control ifie'ir'iber against an increasing tension exerted" by spri g. resistance offered by the spring tolth'er I the loading pulley and the "mcsvmmfpr the. control member is varied by the tensioping mechanism controlled through its associated motor circuit from the indicated air speed motor control circuit of the trainer.

. s merge i the rudder io iiit i loading"naemnrsmsbrisaume the yok orfstik Rte, egrtipn the jeof a 0 ir eeof the trainer and show s inthe lowj portion 4 sociated with the aileron trimming or loading mechanism schematically disclosed in the upper portion of Fig. 8 and shows in the lower portion thereof the motor control circuit and motor for driving the spring tensioning drums of Figs. 6 and 8;

A Fig.3 shows the loading mechanism for loading theailerori' control wh'l'f an'd Fig. 9 shows the indicated air speed motor control circuit of the trainer from which the spring tensioning motor control circuit is controlled.

To better visualize the invention Fig. 7 should be pla e'd beneathFig. 5, Fig. 9 should be placed 7 and Figs. 6 and 8 should be placed on the right of Figs. 5 and '7, respectively.

Referring firstt'o Figs. 1 to l, inclusive, which disclose one of th e trimming or loading mechanismsand in particular the trimming mechanism which is provided for loading the yoke, the.

iro ns'fi figuredtoia horizontally disposed plate 5 and to.

an "thee iron; a. the horizontal 3- being slotted as at 5 W Z Fall a Pla V ew ra lead ng t im i .4 lAi' hows the man s p i a i 2; my}? 2 s sr ssset qna iewtgken a gae th 5 'j' l 4 V I v I for movement along the rods I4 and F1? t 1? f f p tti Yt li 9UP? ,lsad e 99.11 l5fis 'a'tiw'iiiimin arr'iag l9 ii pri' tw i r39 mage h qksn aw y, t9 tas i r ,i bss memberszo 21 Joined attheir'ends by spacers a Wh g? 9 b .etiesee 21 'wfidti 'oi .otherwise secured thereto. 9. F9? 93. 1. 1??? 5 djto h $1, 51 Sh be -'2 by screw 26 are two Fe 41 rier leee aisles ssst ee ines firsupper: g'b'locks, names on one of s i e? i3 i v a]: at atalily disposed rollers 21 and 313.135 @9329 of which aretwo rotatably I :23 landififl. Four similarly E 5. 9 39 -PF 9. 9 .P- fi fi 2 tof'afllT n l s v re mounted I s d lt-$ .9 P h1 9"? H er 23 As best disclosedin 'fi l f meifigfiifidany Hers 29 and iifl'is' disposed iseases-preg me sages; o'frigi'saas'shtvgs M 'ihff'th lowe' fport merea'r stsi'iepies es d 3 t asimilarities?'eaiitrar assc'iiatd lw'i't'h 65 and iengaee-theupper side of the lower rod is in such I a'manner; that the carriage issupported by the rods but is freehto more along such rods.

Positioned between the side members 29 and 2i adjacent the ends thereof are two grooved cable pulleys 3i and 32. Y Each of these pulleys is se- 'oiirjd 'to a'shortshaft (not shown) the ends of which Tarjoiirnaled "in ball bearing assemblies iiidiiriteoi lin'fioi'esf 'inthe si i'e' members 20 and 2|. enerate eam m position by the plasma ate to the side members byscrews 3 5.

For moving the carriage |9 along the rods |4 andv |5 a feed screw 36 is provided which has a threaded engagement with the feed nut 31 secured to the rear face-'ofthe side member2| of the carriage by bolts 38. The feed screw is journaled in a roller bearing assembly (not shown) which is secured to the outer face of the plate 8 of the .left end member ofthe frame by the lag screws 39. Secured tothe' outer end of the feed screw is a driving pulley 40 grooved to receive the V belt 4| which is'driven by the pulley 42 secured to the shaft of a' carriage trimming motor Ml. Themotor Ml' 'is bolted to a mountin plate 43 welded to the upper faces of the frame angle irons l0 and Journaled. in ball bearing assemblies 44 see cured to the outer flanges ofthe-"frame angle irons Hi and |2,and"|| and J3, by the. bolts 45 is a shaft 46. l On one end of the shaft 46 a pulley 41 is secured, the pulley being positioned between" the side members 20 and 2| ,of the carriage .|9 in alignmentwith thepulleysft'l and 32 and with thelowermost portion of its grooved surface in horizontal alignment with the lower: most portion of the grooved surfaces of pulleys 3| and 32 as best disclosed in Fig. ,6. Also se cured to the shaft 46 and positioned between the angle irons In to l3, inclusive, of .the frame isaspur'gear 48. 7 H

. Also journaled in ball bearing assemblies 49 secured to the outer flanges of the angle irons l0 and I2, and H and |3, bythe bolts 5! is a shaft 5|. tioned between theangle irons of the frame is a pinion gear 52 in-mesh with the spur gear 48, and a spurgear 53. Also secured tothe rear end of shaft 5| as-viewed in Fig. 1 isa loading pulley assembly 54. .The pulley assembly 54 asbest disclosed in Figs. 3 and 4 comprises twoouterfiange members 55 and 56 and .two'inner. drumqmembers 51 and 58; the member 51 being secured to the flange member 55 by screws .59, and the; member 58 being secured to the member 5 6 by; screws 60. The flange member 55. is secured to, the flange of a hub member. 6| by screws ,62 and-the hub 6| is secured to the shaft 5| byfa set screw. lhe

flange member 55. and the drum member 51- secured thereto are rotatable on the hub 6| which extends therethrough The two subassemblies of the pulley 54 are adjustably' secured together by two lag screws 63 which extend through, arcuate slotsinthemembers55 and 51 through holes 64 in the drum member58 and into'threaded holes in v the flange member .56. j l v Each of the drum members Hand. 58 is provided with a slot 65 widening out-from a point near. the hub 6| towards the periphery; of the member the walls of the slot being curved as shown atifiand 61in Fig. 3. It is to be noted that the slots. 65 of the tw o drum members 51 and 58 are rotationally displaced with respect to each other and that this displacement maybe changed by the loosening. of jthe lag screws 63 and by rotating v the subasse'mblies" of the pulley 54 with respect to each other for a purpose to ,be later described. 7 j" e I Extending into each'ofthe slots '65 is a cable 68 the end of which extends through aligned holes drilled through the members of the associated subassembly as"showr'rin -Fig,{ 4 and through a hole in the cable support 69. Tlre hole in thecable support 59 is tapered therebyenabling Secured to the shaft 5| and posithe ends of the strands of the cable to be spread out and soldered together. tothuslanchor the end of the cable to the drummember. The'two cables 68 pass over a guide pulley'l'fi and are then clamped together and connected to. one 'endof] a tensioning spring such as is disclosed in Fig.'1A and schematically disclosed in Fig.6. The pulley 10 is journaled upon the end of a stud 'ljtwhich. extends through holes in the vertical flanges] of the upper angle irons wand H and isclamped to the angle iron. H by thenut l2. Thepulley is positioned on the studll between the spacer ';|3 and the nut 14 which nut retain's'the pulley onthestud.

A short shaft 15 is journaled in ball'bearing assemblies 16 secured to the uppersurfaces o f the angle irons I0 and H bythe bolts Ti and has secured thereto an idler gear 18 which meshes with the spur gear 53. Secured-by thejbolt's'lfi. to the L-shaped bracket islamotor M2 having a pinion 8| on its rotor [shaft in mesh with the.

idler gear 18. The bracket 80 has its short or vertical arm welded to the vertical flangeof the angle iron Ill and is braced. by theb race BZQ one end of which is welded to the. horizontal arm of the, bracket and theother end of which'is welded to the underside of .the horiz ontal flanges of the angle irons l2 and 13. 1

Secured to the. outer vertical flangesqof the angle irons H and I3 is an upwardly-and outwardly extending bracket 83 which is braced by braces 84 and 85, each brace havingavertically disposed portion having its lowenedge contoured to be parallel to theupper surface of the bracket. The brace 84 has twoears 86 inturned from its lower edge and secured to :theupper flangesot the angle irons l0 and-Ii bybolts Bfifiand an outturned car 81 which is welded to 1the, ver.., tically disposed portion ofthe bracket 83. The

brace has an ear 88-inturned fromitslower edge and secured to the upper flanges of the angle irons l0 and H by bolts;89;and an outturned ear 90 which-is welded to theyerticallydisposed portion of the bracket 835.; securedxby nuts 9!;

F to the vertically disposed portion of the bracket 83 near the upper corners thereof are two studs on which are rotatably mountedtwo guide pulleys 92, the pulleysbeing retained on the studs by the nuts 93. These pulleys are so positioned as to be in alignment with the pulleys H31, 32

and 41.

Secured to the upper edge ofthe-side'- member 2| of the trimming carriage I9 is a toothed rack 94 which is inmesh with'thepinion 95 mounted on the shaft of the balancing potentiometer Pf. The potentiometerPl issecured to-a bracket 9b fastened-by screws .91: to. the upper flanges. of the angle irons= l-B and II. 1 Also secured'to the side member 2| of the trimming carriage |9 is.a stud 98 which .is effective tooperate one .or the other of the limit switches .Ll anqigLLinthe-tWo-extreme positions of movement .ofath trimming carriage. The limit switches ar supported any suitable manner on the vertical flangeof the angleir on l3. H I H The upper portion of Fig gfi shows schemati cally the manner in'whi'ch the trimming and loading mechanism disclosed in Eigsl'lfto 4,;"inclnsive, may beinstalled in the trainer in connection with the yoke. fiorthis purpose a pulley EEBB is shown connected to the Shara onwhich the yoke or suc IN is mounted and to which pulley a cable 99 is clamped. The cable then extends ver; the "guide pulleys 92 of the'unitover the' pulley 32bf"the trimming carriage, around the pulley 4T- secured flute a not .191 oi fPEKQL idipeieq e m he pull e qontinues jtoj i'gtate it 15 fill il bfi T4; a 7T5, V' i i' s r v d to ccn Edwin-FA lllal l i l i l b T dua l rg fie rj tubes YTZ and VTS are ed l; The amplifier phbe VTI serves tQ in ut fiq n #1; 9 eine it in two 'tq'az p j' e mpl ed v p p transformer Tl tq e; VT Z." The tube yere ct'ifier tarectify the 112 .d 120' t ipd an o' as a. pbsiti've. pbter'itie i t'g the grids of the gasfll 'ed W YTQeh 1 he o pu Potential item. he b YT! s. l o a d hr h the loiver secondary w'inflingof'tra ns fqrmer TI to the conv :01 grid 91: 1m gas-fill edf fiu'be VTS.

nbii j petlem si p e a e y th Wand 'f f l i dl eefie 195: T9- msmng' im irs. iq n n grids o tubes elneously -h fi1pi1ai13i apply tension to the VTQ, VI5 gngj V' I6 is 'Supp-l'd fmm the alterpf cbmmerqial alters ch' pptent t e pr n e s n h .flowerinor ion of Fi as the s o I n,i',sm's except that no I motoi: is v qu,,ed arid the balancing'; pqtelitiijmeter- P1, and 'lirh it fswitches are diive'n bys'haft- 15! eonneeieauy suitable reduc- 70 tiqn gearing Jo-17h peter shaft of the motor M1. This centre} ei-l guit, is; qpnt relled from a control 4 o e omete B5. dri en f om t e ndica d i ed gfineq n Q $.12? spee rpuit Qt h ilzai er as illu ted in par Phe haf fi i; 1 51s 2 be inig g" #914 5; @hsiefieeissieiw esp .inemsqgtrol cir it is .eqhe i i e lu ii i e bd t fn of motor M2 bi the type'fully disclosed in Patent No. 2,428,767,

granted October 14, 1947, to VWVQP." Albert, R. o. Davis, R. H. Gumley and W .V""I-I.'T. Holden. This .fiit

circuitis provided with a direct current motor Milwhich, through a gear-reduction box 900, drives shaft 901 on whichare mounted the variable potentiometer P9, the variable autotransformers VI and-V2 and a pairof limit switches L23andL24. i i

For controlling the motor M9 whereby it may be driven in either direction of rotation, two incoming signal amplifier tubes V2! andVZZ, two

T2! to the anodes of the rectifier tube VT23. The tube VT23 serves as a full wave rectifier torectifythe input potential applied to its anodes and to apply it as positive potentialtoj'the grid of gas-filled tube VI'25. The output potentialfrom tube-V122 is also applied through the lower secondary winding of transformer 'TZItothe control grid ofthe gas filled tube VT26. Filament heating current for all these tubes is supplied from a source of commercial alternating current through'the' windings of power trans-' former T22 and direct current for furnishing grid bias to the control grids of tubes VT25 and VT26 is supplied from thefalternating current source through the power transformer T22 and thedual rectifiertube V'I24.-- Anode potentialis applied to tubesVTZl and VT22 from battery B22 and GG-cycle alternating-current anode potential is --supplied to the anodes of tubes VT25fand VT26 through the halves of the secondary winding of transformer T23, the anode potential supplied to tube VTZt being displaced 180 degreesin phase from the anode potential supplied to tube VT25. The motor M9 is ofthe direct current type, its stator winding being supplied with direct current from the source B2l, overthe contacts of the reversing relay 963'whereby through the operation of the reversing relays 902 and 903 under the control of tubeVTZGthe direction of rotation of the motor may be reversed. The rotor .of motor MS is energized by positive impulses of currentsupplied thereto from the upper secondary-winding of transformer T23 throughrthe fir- .ing of tubeVT25. a

The. apparatus appertaining to'the invention having'now been described it will first be assumed that thepilot has started the traineron a simulated :fiight and that it isbeing operated at a. cruisingqspeed which is indicated to him by .the indicated air speed indicator of the trainer which has attained. a setting through the opera- .tion of the motor -M9 of -the indicated. air .motor'control circuit of Fig.9.

speed :-'j As the'motor M8 rotates the shaft 91H to a position. indicative=ofthe cruising speed ofthe trainer in its simulatedflight, the. brush'of poeter" P1 is applied over a circuit from-- such ''}-the setting of the brush of potentiometer P915 applied from such brush over conductor 156 f through resistance Al I, condenser CH and rheostat RH to ground; -At the same instant po- *tential of phase 2 is applied over a circuit from ground through the right portion of the second- 'ary winding of transformer TM and through-the winding of balancing potentiometer Pl to ground and the potential derived therefrom in accordance with the position of the brush of potentiombrush, through resistance AI 2 and thence through {condenser CI l and rheostat RH to ground;

It is assumed that potential of phase (pl predominates and that therefore a potential of this phase having a value equal to the difference between i the control potential of phase (pl and the balancover itsupper secondary winding steps up potential and applies it through the full wave "rectifier tubeVTlZ upon the control grids of tubes VT and VTISwhere-it appears as a positive potential of phase 2. i

Normal negative biasing potential is applied'to the grids of tubes VTM and VTIE from-the left secondary winding of power supply transformer TIZ and through the right unit of rectifier tube VTI3 so that the tubes VTM and VTI5 are critically biased when no signal is being received. The biasing circuit for tube VTM may be traced from the grid thereof, through resistances 158 and 159 to the slider of rheostat Rl2, over the anodecathode path through the right unit of tube V'IIS, through the left secondarywinding of transformer Tl2, through resistance 160 to the cathode of tube V'IM. A similar biasing circuit extends from'the grid of tube VTI5 through resistances lEil and 159 and thence as traced through resistance 160 to the cathode of tube VTIS j Alternating current potential of 60 cycles plied from a source connected between the terminals 762 and 153 of the primary winding of transformer- TI 3 is impressed upon the secondary winding of such transformer, and such secondary windinghaving its middle point-grounded, potentialsdegrees apart in phase'are derived from the two portions of the secondary winding. Potential of phase q is applied from the left portion oilthe secondarywinding over the right back contact of relay 15d and through choke coil 155 to the anode of tube VTI5 and potential of phase 2 is applied from'the right portion of the, secfondary winding over the left back contactof relay 164 and through choke coil (66 to the anode 'oftubeVT'M. l i Since the tube VTIZ serves as a full wave rec- 'ti-fier, at the instantthe signaling potential appears as positive potential on the gridof tube VTl5 the' anode of tube VTI5 willalso be positive and tube VTI5 will therefore fire and apply'a positive impulse of current over a circuit from ground through-the left portion of the secondary winding of transformer Tl3, over the right back contact of relay 164, through coil 165, over the anode-cathode path through tube VT|5 and through the rotor ofmotor M! to ground Dur ing the next half cycle of the signaling potential when it againappears as a positive potential on the grid of tube VTM, the anode of tube VT! 4 will sna s ming, disclosed in Figf 5, becomes unabalanced.

Alternating current: from the 60-cyclesource connectedbetween terminals 503 and 504 of the primary Winding of transformer T4 and impressed upon the divided secondary winding of this transformer causes potentials 180 degrees apart in phase, which may be termed phase (pl and phase 2,"to be impressed across the terminals of the windings of potentiometers'PI and P2, whereby a potential of phase l is derived from the potentiometer P2 and impressed over a circuit extending from ground, over the left portion of the secondary winding of transformer T4, over the left portion of the winding of potentiometer P2 and the brush thereof, through resistance A2, condenser CI and rheostat RI to ground. At the same time a potential of phase 2 is derived from the potentiometer PI and impressed over a circuit extending from ground over the right portion of the secondary winding of transformer T4, over theleft portion of the windingof potentiometer PI and the brush thereof, through resistance AI, condenser CI and rheostat RI to ground. Since the brush of potentiometer P2 has been assumed to'have" been moved by the elevator trimming wheel 524 to a position to reduce the potential of phase' l and to thereby unbalance the control circuitjpotential of phase 2 will predominate in the-circuit through rheostat RI anda potential, of this phase will therefore be applied to the in-' put grid'bf tube VTI; will be amplified by tube VTI and impressed through the transformer TI and there'ctifler tube VT2 upon the control grids of the gas-filled tubes VT4 and VT5 as a positive signaling potential. At the sametime the signaling potential will also be applied over the lower secondary winding of transformer TI upon the control grid of gas-filled tube VTB.

In the mannerpreviously described in connection with the operation of the control circuit for the spring tensioning motor, the tubes VT4 and VT5 will alternately fire inresponse to the signalwe potential and tube VT6 will also fire since the signaling potential applied to its control grid. is in phase with theyanode potential applied to its anode over the circuit from ground through the right portion of the secondary winding of transformer T3, through the windingof anode relay 520 "and resistance 5I9 in parallel, through the choke'coil 52I to the anode of tube VTB. Con sequently, anode relay 520' and reversing relay 522 are operated and the stator circuit of motor MI isestablished from ground through the source 1 of direct current BI, through ballastresistance lamp '523, over the outer right front contact of relay 522 throughthe stator winding ofmotor Mlj'over the inner right front contact of relay 522, overthe normal contact oflimit switch LI to ground. With the rotor circuit'of motor MI energized'by impulses of positive current transmitted alternately therethrough over the cathode-anode paths through tubes VT4 and VTS, themotoris now driven in'such a direction of rotation as'to rotate the feed screw 36 in a clockwise direction to thereby move the trimming'carriage I9 towards the left as viewed in Fi 6.

As the carriage moves toward the left, the rack 94 rotates the gear 95 and thereby rotates the brush of'the balancing potentiometer Pl in;

a clockwise direction. As' the brush of potentiometeraPI thus moves, the, potential of phase (p2 transmittedthereover through the rheostat RI isdecreased, thereby reducing the unbalance of e the yoke maintains its adjusted position without VT5. The motor MI thereupon slows down and when the brush of potentiometer PI is so posi tionedthat the potential of phase 2 applied thereover'equ'als the potential of phase (pl applied over the brush of potentiometer P2, no signaling potentialwill appear on the grids of tubes VT4 and VT5 and the motor MI will thereupon come to rest.

The movement of the trimming carriage I!) toward the left, tends to rotate the pulley 41 and the pulley, I00 through the pull exerted by the cable 99,-but the pulley 41 is restrained from turning freely by the opposing force exerted through the gear train including the gears 43..

52, 53, I8 and 8| connecting the shaft 46 on which pulley 4' Iis mounted and 'therotor shaft of the dynamic brake motor M2. Consequently pulley I00 rotates in a counter-clockwise direction and moves the yoke IIII to the left or in the direction in which a pilot would move the yoke of an actual aircraft to correct a tendency of such aircraft to nose up. The horizon bar of the train-- erfshould now indicate a simulated level flight.

The yoke will now remain in its adjusted position without the application of any holding force:

thereto by the pilot.

The pilot could of course accomplish the trim? ming of the elevator by first moving the yoke untilthe horizon bar indicates level flight and then operate the elevator trimming wheel until any effort on the part of the pilot.

In a similar manner the pilot may correct any tendency of the trainer to simulate the yawing or rotation of an aircraft about its vertical axis, by the operationof the rudder trimming wheel until the rate of turn indicator indicates a straight line flight. To simulate the trimming of the rudder so that the pilot need not operate. and hold the rudder pedals in the required position to maintain the straight line flight, the pilot operates the rudder trimming wheel where i uponv the control circuit for rudder trimming indicated by the box 550 of Fig. 5 functions to move the trimming carriage of the rudder loading or trimming mechanism from Fig. 6 until the f pedals will attain their required positions without any pressure on them by the pilot.

Also in a similar manner, the pilot may cor- 1 rect any tendency Of the trainer to simulate the. roll or rotation of an aircraft about its longitudinal axis, by the operation of the aileron trimming wheel until the bank indicator or ball indicator indicates that the flight is no longer; banked; To simulate the trimming of theailerons so that the pilot need not operate and hold the-control circuitand thevalue of the signaling the aileron wheel in the required position to correct this condition'of unbalance, the pilot operates the aileron trimming wheel whereupon the control circuit for aileron trimming, indicated by the box "I00 of Fig. 7 operates to move the trim ming carriage of the aileron loading or trimming mechanism of Fig. 8 until the aileron wheel will retain the required position without any oper 1 tion of it by the pilot.

- Having completed the trimming of the trainer, it will now be assumed that the pilot desires to 1 start alongsteady climb to a high altitude. To

accomplish this the pilot increases the air speed whereupon theindicated air speed motor control circuitof Fig. 9 is controlled inaccordance'therewith, and through the new setting of the potentiometer P9 associated therewith causes the 0on5 trol circuit for spring tensioning, disclosed in Fig. 7 to function, in the manner previously de.

arias-3s and to theaileron wheel may be increased or de creased through the operation of the trimming carriages in the manner hereinbefore described, whereby the pilot is enabled to sense the effects which rough air would have on an actual aircraft and to operate the controls to counteract such effects, 7

Since in the operation of an actual aircraft thecontrols would be affected bythe slip stream from the propellers as soon as the engines are started, even through the aircraft does not move and no air speed is developed, provision is also made for applying a fixed potential to the input of the control circuit for the spring tensioning motor to unbalance such circuit and to thereby tension the springs 102, I01 and "l H associated with the yoke, rudder and aileron loading mechanisms; For this purpose, and assuming that the trainer is equipped to simulate the operations of a two-engined aircraft, potential is applied from the brake horse-power motor control circuit T80, through resistance M3, to the input circuit of tubeVTl I' when the right engine is started and potential is applied from the brake horse power motor control circuit 190, through resistance All,

to the input circuit of tube VTII when the left engine is started. Other reactions such as the stalling orthe attitude of an aircraft may be simulated in the trainer by the application of potentials responsive to such eifects through inputresistances such asAll to the input circuit of tube VTH of the control circuit for the spring tensio-ning motor.

Since the failure of either engine of an actual aircraft reacts upon the rudder to cause the aircraft to yaw, provision is made for applying potentials from the brake horse-power motor control circuits 180 and 199- through resistances A1 and A8 to the control circuit for rudder loading or trimming 550.

The position of the wing flaps of an aircraft and. the thrust horse-power developed by the aircraft engines also have reactions on 'theelevator and therefore on theyoke and-these reactions are simulated in the trainer through the application of potential applied from the flap motor control circuit 589 through resistance A4 to the input circuit of tube VI! of the control circuit for elevator trimming and fromthe thrust horse-power motor control circuit 590- through resistance A to the input circuit of tube V'Il.

What is claimed is:

1, In an aircraft trainer, control means cor-'- responding to the control means of an aircraft for moving the steering surfaces thereof, means for applying a steady force opposing the operation of each of said control means in simulation of the forces required to move the steering surfaces when the aircraft is in straight and level flightyan electrical. circuit including means for representing airspeed, and means controlled by said latter means. for applying additional variable forces opposing the movement of said control means simulating the forcesrequired to move the steering surfaces .under varying air speed. conditions. r V 1.,

2. In an aircraft trainer, a yoke corresponding to the elevator control yoke of an actual aircraft, a dynamic brake connected with said yoke for applying a steady force opposing the movement of. said yoke in simulation of the force required to move the. elevator when the aircraft is in straight and level flight, .an electrical circuit including means for representing air speed, and

means. controlled-by said latter means fo'rapply-'- ing an additional variable force opposing the movement of said yoke simulating the force required to move t'he'elevator under varying air speed conditions.

2. "In an aircraft trainer, rudder pedals corresponding'to the rudder pedals of an actual aircraft, a dynamic brake connected with said pedals for applying a steady force opposing the movement of said pedals in simulation of the force required to move the rudder when theaircraft is instraight and level flight, an electrical circuit including means for representing air speed, and means controlled by said latter means ror applying an additional variable force opposing the movement of said pedals simulating the force required to move the rudder under varying I air speed cinditio'ns 4. In an aircraft trainer, an aileron control means corresponding to the aileron control means or an actual aircraft, a dynamic brake connected with said control means for applying a steady force opposing the movement of said control means simulation of the force required to move the ailerons when the aircraft is in straight and level flight, an electrical circuit including means for representing air speed, and means controlled by said lattermeans for, apply ing an additional variable force opposing the movement of said control means simulating the force required to move the ailerons under varying air speed conditions.

5. In an aircraft trainer, a control means corresponding to a steering surface control means of an actual aircraft, a loadingpulley, means for communicating the movement of said control means into a rotation of said pulley, a loading spring, a spring tensioning drum, cables con neeting the ends of said spring with said pulley and with said drum, and means controlled inaccord'anoe with the air speed of the simulated flight being flown by the trainer for rotating said drum to change the tension of said spring whereby a resistance to the rotation of said loading pulley and the movement of said control means is provided which varies with the air speed of the simulated flight.

6-. In an aircraft trainer, a control means corresponding to a steering surface control means of 'an actualaircraft, a, loading pulley, means for communicating the movement of said control means into a rotation of said pulley, a loading spring, a, spring tensioning drum, two cables having one end of each anchored at different points on said pulley and their other ends secured to one end of said spring, a third cable having one end secured to the other end of said spring and its other end attached to and wound on said drum, and means controlied in accordance with the air speed of the simulated flight being flown by the trainer for rotating said drum to change the tension on said spring whereby a resistance to the rotation of said loading pulley in either direction and to the movement of said control means is provided which varies with the air speed of a simulated flight.

'1. In an aircraft trainer, 3', control means corresponding to a steering surface control means or" an actual aircraft, a loading pulley, a driving pulley, speed amplifying gearing interposed between the shafts of said pulleys, a driving cable connecting said control means with said driving pulley, a loading spring; a spring; tensioning drum, cables connecting the ends of said spring with said loading pulley, and with said drum, and. means controlled in accordance with the all? speed of the simulated flight being flown by the trainer for rotating said drum to change the tension of said spring whereby a resistance to the rotation of said loading pulley is provided and communicated from said loading pulley through said gearing, driving pulley and driving cable to said control means, which resistance varies with the air speed of the simulated flight.

8. In an aircraft trainer, a control means corresponding to a steering surface control means of an actual aircraft, a loading pulley, means for communicating the movement of said control means into a rotation of said pulley, a loading spring, a spring tensioning drum, cables connecting the ends of said spring with said pulley and with said drum, a control circuit operable in accordance with the indicated air speed of the simulated flight being down by said trainer, a reversible motor for driving said drum, and a control circuit for said motor operable from said indicated air speed control circuit whereby said drum is rotated in one or the other direction to change the tension of said spring and whereby a resistance to the rotation of said loading pulley and to the movement of said control means is provided which varies with the indicated air speedof the simulated flight.

9. In an'aircraft trainer, a control means corp di g to a steering surface control means of an actual aircraft, a loading pulley, a driving pulley, speed amplifying gearing interposed between the shafts of said pulleys, a driving cable connecting said control means with said driving pulley, a direct current motor having a direct current energizer stator and having a short-circuited rotor, speed amplifying gearing interposed between the shafts of said loading pulley and of said motor, said motor when operated from said control means through said driving cable, driving pulley and gearing serving as a dynamic brake to retard the movement of said control means, a loading spring, a spring tensioning drum, cables connecting the ends of said spring with said loading pulley and with said drum, and means controlled in accordance with the air speed of the simulated flight being flown by the trainer for rotating'said drum to chang the tension of said spring whereby a resistance to the rotation of said loading pulle is provided, and communicated from said loading pulley through said first gearing, driving pulley and driving cable to said control means which resistance varies with the air speed of the simulated flight.

10. In an aircraft trainer, a control means cor' responding to a Steering surface control means of an actual aircraft, a frame, a driving pulley having a shaft journaled in said frame, a trimming carriage movable with respect to said frame and having two pulleys journaled thereon, a driving cable connected to said control means and to said driving pulley and extending over said carriage pulleys, a reversible motor for moving said carriage in either of its directions of movement, a trimming wheel operable to simulate the operation of a trimming tab of thei Y steering surface of an actual aircraft, and a control circuit for said motor responsive to the operation of said trimming wheel whereby said trimming carriage is moved to operate said driving cable and thereby to move said control means to simulate the response of the control means of an actual aircraft to the trimming of a steering surface. 7

11. In an aircraft trainer, a control mean corresponding to a steering surface control means of an actual aircraft, a frame adriving pulley having a shaft journaled in said frame, a trimming carriage movable with respect to said frame and having two pulleys journaled thereon, a driving cable connected to said control means and to said driving pulley and extending over said carriage pulleys, a reversible motor for moving said carriage in either of its directions of movement, a trimming wheel operable to simulate the operation of a trimming tab of the steering surface of an actual aircraft, a, control circuit for said motor unbalanced by the operation of said trimming wheel whereby said trimming carriage is moved to operate said driving cable and thereby to move said control means to simulate the response of the control means of an actual aircraft .to the trimming of a steering surface, and means controlled by the movement of said carriage for balancing said control circuit to stop said motor when said carriage has been moved an amount commensurate with the movement of said trimming wheel.

12. In an aircraft trainer, a control means corresponding to a steering surface control means of an actual aircraft, a frame, a driving pulley having ashaft journaled in said frame, a trimming carriage movable with respect to said frame and having two pulleys journaled thereon, a driving cable connected to said control means and to said driving pulleys and extending over said carriage pulleys, a reversible motor for moving said carriage in either of its directions of movement, a trimming wheel operable to simulate the operation of a trimming tab of the steering surface of an actual aircraft, a control circuit for said motor responsive to the operation of said trimming wheel whereby said trimming carriage is moved to operate said driving cable and thereby to move said control means to simulate the response of the control means of an actual aircraft to the trimming of a steering surface, a rough air circuit, and means control-led thereby for operating said control circuit whereby said trimming carriage is moved to thereby move said control means to simulate the effect of rough air on the control means of an actual aircraft.

' 13. In an aircraft trainer, a control means corresponding to a steering surface control means of an actual aircraft, an electrical circuit including means for representing air speed, means controlled by said latter means for applying a variable force opposing the movement of said control means simulating the force required to move the steering surfaceunder varying air speed conditions, means for simulating the trimming of the steering surface and means controlled by said trimming means to reduce said applied force and to thereby enable said control means to be easily operated.

14. In an aircraft trainer, a control means corresponding to a steering surface control means of an actual aircraft, an electrical circuit including means for representing air speed, means controlled by said latter means for applying a variable force opposing the movement of said control means simulating the force required to move the steering surface under varying air speed conditions, means for simulating the trimming of the steering surface and means controlled by said trimming means to overpower said applied force whereby said control means is operated under the control of said trimming means.

- 15. In an aircraft trainer,'a control means corresponding to a steering surface control means of anactual aircraft, a frame, a loading pulley, a

driving pulley, gearing interposed between the shafts of said pulleys, a loading spring, a spring tensioning drum, cables connecting the ends of said spring with said loading pulley and with said drum, means operable in accordance with the indicated air speed of the flight being flown by said trainer for rotating said drum to tension said spring, a trimming carriage movable with respect to said frame and having pulleys journaled thereon, a driving cable connected to said control means and to said driving pulley and extending over said carriage pulleys whereby said tensioned spring imparts a resistance to the movement of said control means, a reversible motor for moving said trimming carriage in either of its directions of movement, a trimming wheel operable to simulate the operation of a trimming tab of the steering surface of an actual aircraft, and a control circuit for said motor responsive to the operation of said trimming wheel whereby said trimming carriage is moved and through said driving cable to rotate said loading pulley in a direction to reduce the resistance to the movement of said control means imposed by said spring.

16. Aircraft training apparatus comprising a manually actuated control member, means for yieldingly resisting manual movement of said member, an electrical circuit including means for representing air speed, and means operated by a potential derived from said air speed circuit for varying a resistance to movement of said control member. I

1'7. Aircraft training apparatus comprising means forming a motor circuit including an air speed motor, a simulated aircraft control member, an electromechanical device disposed to resist the movement of said control, and means re-- sponsive to a potential derived from the motor circuit for varying the functional effectiveness of said electromechanical device.

18. Aircraft training apparatus comprising simulated flight controls for practicing maneuvers, means for simulating air speed including an electrical circuit energized in accordance with conjoint operation of said controls, means for deriving a voltage from said circuit varying with the simulated air speed, and control-loading mechanism responsive to said voltage for varying the resistance to movement of certain of said controls from neutral in accordance with change in said simulated air speed.

RICHARD C. DAVIS.

VINCENT F. BOHMAN. CHARLES E. GERMANTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,865,828 Buckley July 5, 1932 2,099,857 Link Nov. 23, 1937 2,124,684 Behr July 26, 1933 2,153,986 MacLaren Apr. 11, 1939 2,336,711 Barber Dec. 14, 1943 2,341,253 West Feb. 8, 1944 2,366,603 Dehmel Jan. 2, 1945 2,385,095 McCarthy Sept. 18, 1945 FOREIGN PATENTS Number Country Date 396,540 Great Britain 1933 93 G a B tain 194 

